This invention relates to electro-optical devices whose electromagnetic radiation absorption characteristics can be selectively altered by influence of a suitably controlled electric field. More particularly, the invention is concerned with an electro-optical device which as a display screen with a plurality of dscrete display elements. Still more particularly, this invention is directed to an electrochromic device including a circuit for controlling the display device equipped with an alpha-numeric or an X-Y matrix type display.
In commonly assigned, copending U.S. applications, Ser. No. 41,153, now abandoned, Ser. No. 41,154, now abandoned, and Ser. No. 41,155, now U.S. Pat. No. 3,708,220, all filed May 25, 1970, and U.S. Pat. Nos. 3,521,941 and 3,578,843, there are described electro-optical devices exhibiting a phenomenon known as persistent electrochromism wherein electromagnetic radiation absorption characteristics of a persistent electrochromic material are altered under the influence of an electric field. Such devices are employed in sandwich arrangement between two electrodes. Coloration is induced by charging the electrochromic film negative with respect to the counter-electrode, employing an external potential. The counter-electrode can be the same as the persistent electro-chromic material or different.
By reversing the original polarity of the field or by applying a new field, it is also possible to cancel, erase or bleach the visible coloration.
These steps of color induction and erasure are defined as cycling.
The devices described in the prior applications are effective to change their electromagnetic radiation transmitting properties under the influence of an electric field, but the practicality of a simple sandwiched or layered arrangement of electrodes and layer of electrochromic material is somewhat limited due to the fact that prior devices were either simple area displays or devices with separate characters.
It is therefore an object of this invention to provide an electrochromic imaging device having a plurality of discrete display areas.
A further object is to provide such an electrochromic device with means to multiplex the display.
These and other objects of the invention will become apparent as the description thereof proceeds.